Pulse forming networks are frequently employed to supply short duration, high voltage pulses to various types of loads, such as magnetrons. The pulse forming networks are usually charged from a complex, high voltage DC source, such as a 10 kilovolt source, connected to a step up transformer by way of a switch. It is a requirement for the pulse forming network output voltage to achieve a precise value. Previously "De-Qing" circuits have been used to enable the precise pulse forming network voltage to be achieved. A De-Qing circuit uses a second, separate network to remove excess energy from the pulse forming network. The excess energy is dissipated in resistors forming part of the De-Qing circuit. Hence, the prior art arrangement is relatively inefficient and requires a significant number of components. Typical prior art De-Qing circuits are disclosed in the following publications: "A Unique Regulator by De-Qing Method," Slampyak, 1966, pages 482-489, Ninth Power Modulator Symposium; "High-power Pulse System Regulation," Schonberg, 1960, pages 313-322, Sixth Power Modulator Symposium; "Design for the Stanford Two Mile Linear Accelerator," Smith, 1962, Seventh Power Modulator Symposium, pages 312-320, and "Secondary Pulse Voltage Regulation," Voak, 1966, Ninth Power Modulator Symposium, pages 464-480.